How do i get these cracks to disappear?
If you use the Cell fracture addon, there is an option called Margin. It sets the space ('cracks') between the fractals. If you see these cracks, the reason may be that your Margin is set too high.

Ensure, that it is not too small, because otherwise the physics engine thinks that the parts are intersecting each other, calculate a repelling force and this will tear the the ball apart.